GFP expression from plasmids containing synapsin promoter. (A, B, C, D, and E) Expression of GFP with synapsin promoter plasmids. 293T cells were transfected with no plasmid (A), Lv-Kir2.1 (B), Lv-synapsinP-Kir2.1 (C), Lv-ΔCMV-synapsinP-Kir2.1 (D), or Lv-ΔCMV-LTR-RRE-cPPT-synapsinP-Kir2.1 (E). Images were taken after 24 h under a microscope (IX70 Olympus). Bar, 50 μm. (F) Summary of GFP expression analyzed with the ImageJ software. The whole-cell area of each cell was manually selected, and the average gray value (n = 50, from three independent experiments) is presented as the fluorescence in arbitrary units (au) of the software (p < 0.000000001, ANOVA). Note the moderate GFP expression in the Lv-synapsinP-Kir2.1-transfected cells (p < 0.005 vs mock transfection; post hoc Student’s t test) and its slight expression in the Lv-ΔCMV-synapsinP-Kir2.1- (p < 0.01) and Lv-ΔCMV-LTR-RRE-cPPT-synapsinP-Kir2.1-transfected cells (p < 0.05). The GFP expression in the two ΔCMV-plasmids-transfected cells was lower than that in the Lv-synapsinP-Kir2.1-transfected cells (p < 0.005). Schematic illustrations show the difference in plasmid construction.